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Rh of it, and of many of the men and ships that made it what it was.

Of late years there has been a confusing mixture of the terms knot and mile as applied to the speed of vessels. As most persons are aware, there are three kinds of mile: the geographical, statute, and sea mile or knot. The geographical mile is based on a measure upon the surface of the globe, and is a mathematical calculation which should be used by experts only. The statute mile, instituted by the Romans, is a measure of 5280 feet. The sea mile or knot is one sixtieth of a degree of latitude; and while this measurement varies slightly in different latitudes, owing to the elliptical shape of the globe, for practical purposes the knot may be taken as 6080 feet.

The word knot is now frequently used to express long distances at sea. This is an error, as the term knot should be used only to denote an hourly rate of speed; for instance, to say that a vessel is making nine knots means that she is going through the water at the rate of nine knots an hour, but it would be incorrect to say that she made thirty-six knots in four hours; here the term miles should be used, meaning sea miles or knots. The term knot is simply a unit of speed, and is derived from the knots marked on the old-fashioned log line and graduated to a twenty-eight-second log glass which was usually kept in the binnacle. In this book the word mile means a sea mile and not a geographical or statute mile.

I wish to make my grateful acknowledgment to the Hydrographic Office at Washington, the British